1. Field of the Invention
The present invention generally relates to a resetting circuit for a microcomputer. More specifically, the present invention is directed to a resetting circuit for a low consumption current device including a microcomputer to which a voltage is applied from a battery, and which functions as a controller, for instance, directed to a resetting circuit of a microcomputer in a remote control device or the like.
2. Description of the Prior Art
In an apparatus including a microcomputer, or microprocessor functioning as a controller, it is necessary to reset an internal circuit condition of this microcomputer by generating a reset signal after a predetermined time has passed since a predetermined voltage was applied to the microcomputer when the microcomputer was energized by a power source.
To this end, a time constant circuit is employed in such an apparatus. After a predetermined time has elapsed since the microcomputer was energized, the voltage across capacitor terminals of the time constant circuit is preset to be higher than a given threshold level. As a result, a reset signal is changed from a low level to a high level, which enables the microcomputer to be reset.
To reset the microcomputer every time the microcomputer is energized by a power supply, the signal level of the reset signal (i.e., the voltage across the capacitor terminals) must be low.
However, in a low consumption current circuit such as a remote control apparatus employing a battery as a power source, a current discharged from the capacitor is extremely low when the power source is disconnected from the low consumption current circuit, and also a considerably long time period is required until the terminal voltage of the capacitor is lower than the predetermined threshold level. In other words, a substantially long time has passed in order that the reset signal becomes a low level. Under these conditions, if the power switch is turned on before the reset signal becomes a low level, the microcomputer cannot be set and may be brought into an erroneous operation because the signal level of this reset signal cannot be changed from the low level to the high level.
It is therefore an object of the present invention to provide a resetting circuit for a microcomputer, even if it is constructed of a low consumption current circuit, capable of resetting the microcomputer when it is energized by a power source.